I. ABSTRACT Although men who have sex with men (MSM) have the highest HIV prevalence in Peru, they are underserved by traditional preventive programs. Interestingly, in Peru the Internet has emerged as an effective, and convenient tool to reach this population. A recent study on MSM conducted by our group, demonstrated the feasibility of conducting an online randomized controlled trial to test the effect of a brief health promotion video in increasing HIV testing among MSM. The proposed study is designed to develop and test the effectiveness of a novel web-based HIV intervention that includes the delivery of videos tailored to each of the barriers/reasons MSM have for not getting tested for HIV as well as HIV testing motivational messages sent via mobile-phone text messaging, e-mail or instant messaging robots. The intervention and assessments will be guided by the Information- Motivation-Behavioral skills model, the Health Belief Model and the Stages of Change theory. The control intervention will be a health promotion message (similar in content to other Peruvian websites) with an invitation for free HIV testing. Testing will be offered at the Via Libre clinic and two mobile units whose location will be determined based on participants' demand. Participants from both intervention arms will be asked to complete follow-up assessments at the 7th day, 30th day and 6th month after the intervention. The outcomes evaluated will be intention to get tested and actual HIV testing among MSM of each of the trial arms. If this novel web-based intervention is effective in increasing HIV testing among high-risk MSM, it could be adopted by HIV and STI prevention programs.